Effects of core-shell polycarboxylate superplasticizer on the fluidity and hydration behavior of cement paste

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 2020-04, Vol.590, p.124464, Article 124464
• Main Authors: Chen, Shengli, Sun, Shenmei, Chen, Xiaolong, Zhong, Kaihong, Shao, Qiang, Xu, Haijun, Wei, Jiangxiong
• Format: Article
• Language: English
• Subjects: Cement; Fluidity retention; Nanomicelles; Polycarboxylate superplasticizer
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/j.colsurfa.2020.124464

The polycarboxylate superplasticizer nanomicelles (nano-PCEs), prepared by aqueous emulsion copolymerization, continuously release absorbable carboxyl groups with the hydrolysis of poly(hydroxyethyl acrylate) segments and the dissociation of nanomicellar crores, exhibiting an excellent fluidity retention for cement pastes. [Display omitted] •The polycarboxylate superplasticizer nanomicelles with hydrolysable cores were prepared via emulsion copolymerization.•The slow release of carboxyl groups is modulated with polystyrene segment for fluidity retention.•The fluidity of cement paste is maintained in 3 h with a nano-PCE dosage of 0.20 % bwoc and a water/cement ratio of 0.35. Polycarboxylate superplasticizer nanomicelles (nano-PCEs) with a core-shell structure were prepared via aqueous emulsion copolymerization in one pot. The shells are constructed with hydrophilic segments of poly(acrylic acid)-co-poly(isobutenyl polyethenoxy ether) (PAA-co-PHPEG), offering the water-reducing performance and stability for nano-PCEs. The cores are self-assembled with hydrophobic segments of polystyrene-co-poly(hydroxyethyl acrylate) (PS-co-PHEA), endowing nano-PCEs with good loss resistant of fluidity for cement pastes. The chemical structure of nano-PCEs was verified by the nuclear magnetic resonance spectrum (1H NMR) and fourier transform infrared spectroscopy (FTIR), and the 16−48 nm diameter of nano-PCE nanomicelles was determined by dynamic laser scattering (DLS) and transmission electron microscopy (TEM). Compared with comb PCEs, the cement paste containing nano-PCEs exhibited better fluidity retention of three hours by mini-slump measurements, lower hydration heat and more delayed hydration heat evolution by isothermal calorimetry tests. Furthermore, the hydrolysis and adsorption behavior of nano-PCEs in alkaline cement pastes were deduced, and a working mechanism of nano-PCEs was theoretically explained. This new type of superplasticizer nanomicelles can be used as a long time rheology modifying agent in fresh cementitious systems.